Answered: 4 of the most common fuel octane questions | Fuel Facts

Which nozzle should you grab when filling up?

When in doubt, read the owner’s manual. There should be one sitting inside the glove box. Assuming we’re talking about a stock, production street vehicle, the owner’s manual will explain which fuel to use–but, of course, questions might still remain. 

Are All Octane Numbers Equal?

In the U.S. and Canada today, gasolines are rated on the Anti-Knock Index (AKI). That’s the figure found on our pumps and inside the owner’s manual. 

The worldwide standard, however, is the Research Octane Number (RON), so you might also find this one listed in the owner’s manual, particularly for an older foreign car. The manual for our U.S.-spec 1984 Porsche 911 Carrera, for example, lists both minimums: 91RON or 87 AKI. 

What If the Local Stations Don’t Offer Enough Octane?

At higher elevations, you might notice octane minimums that are lower than the national norms, meaning premium fuel rated at 91 versus 93.

Why is that? Less barometric pressure requires less octane. Again, the owner’s manual should provide some guidance here, where most new cars can recalibrate their engines to eliminate the knocks and pings often associated with the preignition caused by too little octane. 

What About Using Too Much Octane?

Some of us have heard the rumors: Running too much octane will actually decrease performance. Extra octane is like having extra insurance. High-octane fuel is also a more refined product, meaning it will age better and leave less deposits than a lower-grade product–big benefits for a car that might sit for a bit. 

Another related note: The recipe for the fuel sold at the local station can vary depending on season, retailer or location. All Sunoco Race Fuels, though, are blended to the same formula with no deviation.

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